Week 3 embryo

Question 1

3 facts about the embryonic period

Answer 1

1. 3-8 weeks of development
2. time of greatest organogenesis
3. stage when most susceptible to teratogens

Question 2

primitive streak formed by epi or hypoblasts?

Answer 2

epiblasts

Question 3

primitive streak defines which axis of the embryo?

Answer 3

cranial- caudal

Question 4

epiblasts travel through ___ to make mesoderm and endoderm

Answer 4

the primitive groove, where epiblasts displace hypoblast layer to form ectoderm and fill in the space between the two layers to make mesoderm/ mesenchyme

Question 5

gastrulation occurs in week…

Answer 5

3

Question 6

2 places where there is no mesoderm

Answer 6

oropharyngeal membrane and cloacal membrane

ectoderm and endoderm are tightly fused here.

Question 7

notochord is made by ____ cells

Answer 7

mesenchymal cells that proliferate from the primitive node

Question 8

what does the notochord form in the adult?

Answer 8

nucleus pulposus of vertebral bodies

Question 9

a few facts about the notochord

Answer 9

defines cranial-caudal axis

primary inductor of embryo

forms the nucleus pulposus in adults

induces ectoderm to form the neural plate

made of mesenchymal cells

Question 10

neural tube forms by…

Answer 10

proliferation of ectoderm cells that invaginate and fold on each other

induced by the notochord

Question 11

3 parts of mesoderm

Answer 11

paraxial mesoderm

intermediate mesoderm

lateral mesoderm

Question 12

paraxial mesoderm derivatives

Answer 12

somites (give rise to axial skeleton- skull and vertebrae, muscles, and dermis)

Question 13

lateral mesoderm derivatives

Answer 13

somatic layer- body wall

splanchnic- embronic gut wall

Question 14

2 neuropores of neural tube

Answer 14

1. rostral

2. caudal

Question 15

failure of rostal neuropore to close

Answer 15

anacephaly- brain is exposed :(

Question 16

failure of caudal neuropore to close

Answer 16

spina bifida- spinal cord exposed to amniotic fluid and is damaged

Question 17

derivative of neural tube

Answer 17

brain and spinal cord

Question 18

neural crest cell derivatives

Answer 18

DRG
ganglia of ANS
adrenal glands
cranial nerves
facial muscles
melanocytes

Question 19

intraembryonic coelom formed by the ___ mesoderm

Answer 19

lateral

Question 20

intraembryonic coelom becomes the…

Answer 20

pericardial cavity
pleural cavity
peritoneal cavity

Question 21

angiogenesis begins in the…

Answer 21

extraembryonic mesoderm

yolk sac

connecting stalk

chorion

and grows towards the embryo

Question 22

what are blood islands?

Answer 22

extraembryonic mesenchymal cells that aggregate

Question 23

cardiac mesenchyme forms 3 things:

Answer 23

1. aorta
2. pulmonary a.
3. heart

Question 24

when does the heart begin to beat?

Answer 24

week 3, making it the first functional organ in the embryo